Document scanners have become a popular computing accessory both in the home and the office. Essentially, document scanners (or simply “scanners”) come in three distinct varieties: sheet-fed scanners 210 as shown in FIG. 1, platen scanners 220 shown in FIG. 2, and scanners 230 having a rigid combination of sheet-fed and platen scanning capabilities shown in FIG. 3. With respect to sheet-fed scanners 210, an image-forming subsystem, such as a camera, typically a linear imaging sensor and a lens in combination with an illumination source, scans an image by moving a sheet of paper past the camera, which sits in a stationary position. The documents are fed from a stack and are passed through a paper path disposed at the field of view of the camera. As each document passes in front of the camera individual raster lines are imaged by the camera and then pieced together to create a 2D image representation of the original document. The camera captures the width of the image, line by line, while the document is moved past the camera.
With respect to platen scanners 220, a document is placed face down onto a stationary flat transparent surface of the scanning unit and the image-forming subsystem, camera and illumination source, moves underneath the fixed document to perform the scanning operation. In this case, the camera is moved the length of the document while the camera's optics covers the width of the scanned document. The platen scanner requires lifting a lid and placing document sheets face down one at a time. The platen capability is also employed to deal with documents that do not feed from a stack reliably.
Scanners vary in speed, function, and cost and are often used by businesses for scanning large quantities of documents. The demand for scanning at a given installation can be as high as from several hundred (100) to several hundred thousand (100,000) pages per day. Sheet-fed scanners offer greatest productivity by employing an imaging system on both sides of the paper path, imaging both the front and back of each document during the same scanning operation. One type of production scanner 230 attempts to combine the functionality of a sheet-fed scanner with that of a platen scanner. Essentially, such combination production scanners are manufactured as a single unit that combine the platen scanning functions with the sheet moving functions in a single box.
With prior sheet-fed, platen, or combination scanners, the user must select one type in favor of another. For those customers whose primary need is for a sheet-fed scanner but who occasionally need the platen utility, they must purchase a combination device or two separate scanners (one sheet-fed and one platen). Purchasing both types of scanning devices may be cost prohibitive or impossible and, in either case, impractical for applications where portability is desired. For example, a scanning service provider may require the ability to carry the scanner and host computer in order to transport both systems to a remote jobsite. After the job is finished, the scanner and computer must be brought back to the service bureau headquarters or to the next jobsite. One task may require scanning a large number of similar documents, suited to the sheet-fed scanner and not requiring a platen. The next task at the next site may require scanning fragile documents or books, requiring the use of a platen. Thus, portability and the ability to reconfigure and perform multiple scanning functions are critical to people who buy scanners to scan documents as a service.
Other limitations of the prior art combination production scanners that combine platen and sheet feeding functions in one unit are the relatively high cost and large size of the combined form. Since the form is larger, the cost of manufacture is increased over the single function scanning device. Typically, such combination production scanners only come in one of various classes suitable for scanning a single size or style of document. For example, the platen portion of one combination scanner can be equipped to handle 8½×11 inch and the European equivalent A4 sized documents. The platen portion of a different model is equipped to handle 11 by 17 inch and the European equivalent A3 sized documents. Thus, a given prior art combination production scanners may not be configured to scan the size of documents that the customer desires to scan.
As such, a relatively low cost scanning device that can be had to handle various paper sizes in a unit having a minimum sized footprint, and which combines the functionality of a platen scanner with that of a sheet-fed scanner, and which offers significant flexibility in situating the platen portion relative to the sheet-fed portion, would provide numerous advantages.